(1) Field of the Invention
The present invention relates to a device control apparatus and method of controlling parallel execution of device-control instructions to a plurality of devices of a system.
An information system such as a digital switching system is constructed with a plurality of devices to provide various functions. Recently, it is required that the information system be enabled to efficiently execute a device-control instruction such as placing in service, isolating or switching to any of the devices of the information system. It is desirable to easily carry out an instruction execution control of the devices of the information system.
(2) Description of the Related Art
A conventional digital switching system is one of information systems, and, generally, it is constructed with a plurality of main control devices (such as central processing units), a plurality of main storage devices, a plurality of switching network control devices, a plurality of switching networks, a plurality of channels, and a plurality of external devices (such as magnetic disk units). Various functions of the system are provided by the above-mentioned devices.
In the conventional digital switching system, a device-control instruction such as placing in service, isolating or switching to a single device is executed in accordance with a program of a corresponding central processing unit which controls the device. Since the central processing unit controls a plurality of devices connected thereto, it executes one of device-control instructions to respective devices at a time.
When a competition state between two or more devices with respect to device-control instructions by the central processing unit has occurred, a detection of the competition state is performed by individual programs for the two or more devices in a parallel manner.
As described above, in the conventional digital switching system, one of device-control instructions to two or more devices is executed at a time. There is a problem in that it takes a long time to execute placing the two or more devices in service. In addition, since the individual programs for the two or more devices perform in parallel detections of the competition states of the devices, it is necessary that the programs include a complicated routine in order to perform such detections. Further, it is difficult for the conventional digital switching system to provide a flexibility when adding a new device to the system is required.